After ‘ignoring half the market,’ publishers are targeting women readers with the next generation of book-length comics.

Raina Telgemeier started reading comics at age 9. She began drawing them about two years later, around the time she took a tumble, while chasing a friend, and knocked out her two front teeth.

When she began working as a professional cartoonist in her 20s, she discovered there wasn’t much of a market for the kinds of stories she wanted to tell—stories about her own childhood. At the time her first graphic novel, “Smile,” was published in 2010, comics and graphic novels still skewed heavily toward young men, with an...